HTTP pinger hangs

[davepacheco]

With #78 fixed, I went to try using the pinger again with cueball 2.2.0, but I found that HTTP requests were all queueing up. The pinger requests appear to have hung.

According to @arekinath, this is because of an argument mix-up that causes the agent to use the claim handle is if it were the socket. Nothing in Node's HTTP or socket implementations seem to notice this, but our callback is never invoked.

[arekinath]

The node http logic simply checks socket.writable, and if it's non-truthy (which it is, it's undefined), then it registers a handler on .on('writable', ...) -- which works fine, because the ClaimHandle is an EventEmitter. It'll just never emit that. So we're stuck. Forever.